340 



THE CYCADALES 



slightly modified, the sporangia being developed on their margins, 

 (Fig. 245, 3-B). The microsporophylls are small and more com- 

 pactly arranged, the sporangia being associated in sori on the 



Fig. 245. Sporophylls and sporangia of the Cycads: 2, strobilus of Zamia. 

 2A, cross-section of strobilus of Zamia, showing arrangement of microsporo- 

 phylls. 25, microsporophyll enlarged, showing sporangia arranged in sori. 

 2C, sorus of three sporangia that have opened. 2D, microsporophyll of 

 Cycas. 3, cross- section of a strobilus of Zamia, showing arrangement of 

 megasporophylls. 3^, megasporophyll enlarged with two sporangia. The 

 one on the right shown in section; ms, megaspore; i, integument; sp, spor- 

 angium; m, micropyle. 3B, megasporophyll of Cycas with laterally ar- 

 ranged megasporangia. — H. O. Hanson. 



lower surface of the sporophylls (Fig. 245, 2D). In Zamia, the 

 strobili and sporophylls are quite suggestive of Equisetum, the 

 sporangia being developed on the inner side of shield-like sporo- 

 phylls (Fig. 245, 2-2,A). 



The microspores originate and are discharged from the spo- 

 rangium very much as in the Ophioglossales. The megasporan- 

 gia, however, present several new departures that must be borne 

 in mind. A rather thick coat or integument covers the sporan- 

 gium save for a small opening called the micropyle (Fig. 245, ^A). 

 The integument will be a feature in all the succeeding groups and 



